JPH06292014A - Picture processor - Google Patents

Abstract

PURPOSE:To obtain a picture processor with an optional filter effect by revising a coefficient of a spatial filter in response to a luminance of an input picture to attain gradation correction matching a human visual characteristic. CONSTITUTION:A coefficient signal suitable for gradation correction in a low luminance area is set to a register 7 and a coefficient signal suitable for gradation correction in a high luminance area is set to a register 8 from a CPU 10 as initial setting. A luminance signal of a picture signal from a camera 1 is given to a comparator 5 via an A/D converter 2, compared with a reference value and the result of discrimination of the high and low luminance is given to a selector 9. The selector 9 reads a coefficient signal from the register 7 when the result of comparison indicates a low luminance and reads a coefficient signal from the register 8 when the result of comparison indicates a high luminance to revise a coefficient of a spatial filter arithmetic operation section 6. Thus, gradation is corrected from a luminance signal at a low luminance part and a high luminance part of an input picture with a coefficient suitable for gradation correction respectively and a picture with a gradation suitable for a human visual characteristic is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for filtering an input image to correct gradation.

[0002]

2. Description of the Related Art In the conventional gradation correction, the luminance distribution from low luminance to high luminance is uniformly changed. For example, in FIG.
In the case of the input image having the brightness distribution shown in (a), the direct current component is subtracted from the image signal ((b) in the same figure), and the effective brightness range R of the image signal is multiplied by the brightness direction constant to be shown in (c). The image signal in which the luminance change shown in FIG.

On the other hand, since the actual human visual characteristics have a logarithmic sensitivity to the brightness, the lower the brightness, the more sensitive the brightness is to changes. Therefore, in the gradation correction described above, since the correction is performed uniformly from low brightness to high brightness, if the correction is performed in accordance with the low brightness portion, for example, the desired gradation cannot be obtained in the high brightness portion. If the correction is performed in accordance with the high luminance portion, noise may be emphasized in the low luminance portion. There is also known an image processing method in which each brightness value of an input image is converted into an arbitrary brightness value by using a look-up table, and for example, logarithmic function density conversion is enabled.

[0004]

However, if each luminance value is converted into an arbitrary luminance value by using a look-up table, the necessary image information is non-linearly converted, so that the image information cannot be maintained. is there.

The present invention has been made in view of the above circumstances, and provides an image processing apparatus capable of gradation correction according to human visual characteristics and having an arbitrary filter effect. The purpose is to

[0006]

In order to achieve the above object, an image processing apparatus according to claim 1 inputs an image signal having a luminance value corresponding to an original image and filters the image signal. In the case of performing a process and performing a desired gradation correction, a plurality of coefficients in the i-th row and the j-th column are set, and each of the coefficients is changed in at least one pixel unit according to the coefficient signal, and spatially relative to the image signal. Spatial filter that performs various filtering processes, coefficient storage means that stores a plurality of coefficient signals for setting the respective coefficients in the spatial filter, and detects and detects the luminance value of the image signal input to the spatial filter. Comparing means for comparing the luminance value with at least one reference value set in advance, and in each of the high luminance portion and the low luminance portion of the image signal based on the comparison result of the comparing means, Composed coefficient signal number storage section; and a coefficient selecting means for selectively providing to said spatial filter.

According to a second aspect of the present invention, in the image processing apparatus, a filter calculation coefficient of i-th row and j-th column which can be changed in synchronization with at least one pixel-unit filtering calculation operation is set, and the image signal is at i-th row and j-th column. A spatial filter for inputting in the state of a pixel matrix and performing a filtering process with the filter calculation coefficient centering on a pixel of interest of the pixel matrix, and a plurality of sets of filter calculation coefficient patterns of i rows and j columns to be set in the spatial filter are stored. The coefficient storage means and the luminance value of the image signal input to the spatial filter are detected, the detected luminance value is compared with at least one preset reference value, and the luminance value is predetermined according to the comparison result. Comparing means for outputting the coefficient selection signal, and a filter calculation coefficient pattern from the coefficient storage means based on the coefficient selection signal output from the comparing means. A coefficient selecting means for selecting a filter calculation coefficient pattern and setting the selected filter calculation coefficient pattern in the spatial filter, and a gradation compressing means for performing gradation compression processing on the signal output from the spatial filter. Composed.

[0008]

In the image processing apparatus according to the first aspect, the low-luminance part and the high-luminance part of the input image are detected by the comparing means, and the low-luminance part and the high-luminance part are selected by the coefficient selecting means. The coefficient signal is supplied from the coefficient storage means to the spatial filter. Therefore, different gradation corrections can be performed on the low-luminance portion and the high-luminance portion of the input image by the spatial filter, and since the spatial filtering processing is a linear conversion, the image information is also maintained. .

In the image processing apparatus according to the second aspect, the coefficient pattern corresponding to the brightness value of the image signal is set in the spatial filter, and the result of the filtering process with the coefficient of the pattern different according to the brightness value is performed by the gradation compression means. The gradation is compressed. Therefore, for example, if a high-luminance portion or a low-luminance portion where gradation information is likely to deteriorate when gradation compression is performed, a coefficient pattern with a high degree of gradation enhancement is set in the spatial filter, It is possible to perform gradation compression without degrading gradation information.

[0010]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows functional blocks of an image processing apparatus according to the first embodiment of the present invention. The image processing apparatus of this embodiment is
The brightness signal of the image signal corresponding to the subject image captured by the camera 1 is converted into a digital signal by the A / D converter 2, and the digitized image signal is input to the spatial filter block 4 via the delay unit 3. is doing. In addition, A / D converter 2
The luminance signal of the image signal output from is input to one input terminal of the comparator 5. The comparator 5 has a reference value set to the other input terminal, compares the reference value with the signal value (luminance value) of the luminance signal, and inputs the comparison result to the spatial filter block 4.

Due to the delaying action, the delay section 3 sequentially outputs the luminance signals for seven lines which are continuous in the vertical direction in the input image in parallel from the first pixel simultaneously in each line. Further, the delay unit 3 gives the image signal to be filtered to the spatial filter operation unit 6 in synchronization with the timing at which the coefficient signal corresponding to the brightness determined by the comparator 5 is output to the spatial filter operation unit 6. There is.

The spatial filter block 4 includes a calculation unit 6 (hereinafter, referred to as a calculation unit) for performing a spatial filtering processing calculation.
Referred to as the spatial filter operation unit 6), the first register 7,
The second register 8 and the selector 9 are provided.

The output of this spatial filter block 4 is D
It is output to the monitor 12 via the / A converter 11. In addition, the image signal output from the camera 1 is input to the sync separation circuit 13, and the sync signal separated from the image signal is input to the PLL 1
I am typing in 4. Then, the timing control signal generated by the PLL 14 based on the synchronization signal is used as the A / D converter 2,
Delay unit 3, spatial filter calculation unit 6, D / A converter 11
The operation timing of each part is sent to.

Here, a specific configuration example of the spatial filter block 4 will be described with reference to FIGS. 2 and 3. The spatial filter-block 4 used in this embodiment is divided into first to seventh blocks 21-1 to 21-7. The pixel signal of the first line is input to the first block 21-1 out of the pixel signals of the continuous 7 lines of the input image, and the 2nd to 7th blocks 21-2 to 21-7 have 2 lines. Each pixel signal of the 7th to 7th lines is input respectively. The structures in the first to seventh blocks 21-1 to 21-7 are the same as each other.

FIG. 3 shows the configuration of the first block 21-1. The first block 21-1 includes seven data latch circuits 22-1 to 22-7 connected in series, and the data latch circuit 22- arranged at the input side end portion.
The image signal from the delay unit 3 is first input to 1.

The pixel signals input to the block shift the seven data latch circuits 22-1 to 22-7 by one pixel, and seven pixel signals continuous in one line are transferred to the first block 21-1. Set.

Each of the above data latch circuits 22-1 to 22-
7 are provided with multiplication units 23-1 to 23-7. The seven consecutive pixel signals latched by the data latch circuits 22-1 to 22-7 are multiplied by the set coefficient. Each multiplication unit 23-1 to 23-
The product output from 7 is input to the adder 20 shown in FIG.

Coefficient register groups 24-1 to 24-7 are provided corresponding to the multiplication units 23-1 to 23-7. Each coefficient register group 24-1 to 24-7 is composed of the above-mentioned first register 7 and second register 8, respectively.
That is, the first register 7 and the second register are provided for each coefficient register group. In FIG. 1, only one set is shown and the others are omitted.

In this embodiment, a coefficient signal suitable for gradation correction of the low luminance part of the input image is set in the first register 7, and a gradation signal of high brightness part of the input image is corrected in the second register 8. Set the appropriate coefficient signal. The coefficient signals are set in the registers 7 and 8 from the CPU 10 via the data bus.

Selectors 25-1 to 25-7 are provided for the respective coefficient register groups 24-1 to 24-7. In addition,
In FIG. 1, only one selector is shown and the others are omitted. Each of the selectors 25-1 to 25-7 is composed of the selector 9 shown in FIG. The selectors 25-1 and 25-2
5-7 are coefficient register groups 24-1 and 24-2 corresponding to each other.
It is connected to each register 4-7. These selectors 25-1 to 25-7 correspond to the corresponding coefficient register group 24-
The coefficient of which register is selected from the first and second registers 1 to 24-7 is determined by the comparison result signal provided from the comparator 5.

The coefficients selected by the selectors 25-1 to 25-7 are passed through the coefficient latch circuits 26-1 to 26-7 provided corresponding to the selectors 25-1 to 25-7, respectively. It is given to the multiplication units 23-1 to 23-7.

The second to seventh blocks 21-2 to 21-2
In 1-7, low-luminance and high-luminance coefficients are also stored in the first and second registers of each of the seven coefficient register groups, and the corresponding selector receives the comparison result signal. It is selected and given to the corresponding multiplication unit.

Since the comparison result is output from the comparator 5 in pixel units, the spatial filter block 4 can change the 7 × 7 coefficient in at least one pixel unit. In the adder 20, the sum of the products (pixel values × coefficients) output from the multipliers of the blocks 21-1 to 21-7 in the spatial filter operation unit 6 is obtained.

The added value in the adder 20 may be negative depending on the coefficient selected from the coefficient register group. In this embodiment, the carry of the added value is carried out so that the added value output from the adder 20 is always positive. That is, several types of positive coefficients are stored in the coefficient register group 27 connected to the data bus. Then, the selector 28 selects a predetermined coefficient from the coefficient register group 27, and the selected coefficient is input to the adder 20 via the coefficient latch 29 to be added.

Next, the operation of this embodiment configured as described above will be described. First, as an initial setting, the CPU
A coefficient signal suitable for gradation correction in the low luminance area is set from 10 to the first register 7, and a coefficient signal suitable for gradation correction in the high luminance area is set in the second register 8. Further, the CPU 10 sets a reference value for determining the brightness of the input image in the comparator 5 from the CPU 10.

Next, the image signal of the input image output from the camera 1 is converted into a digital signal by the A / D converter 2. The luminance signal of these is given to the comparator 5 and compared with the reference value. By the comparison, if the luminance value of the luminance signal is larger than the reference value, it is determined to be high luminance, and if it is lower than the reference value, it is determined to be low luminance.

Comparator 5 for judging whether the brightness of the input image is high or low
The comparison result of is given to the selector 9. When the comparison result of the comparator 5 is low luminance, the selector 9 reads the coefficient signal from the first register 7 and sets the coefficient signal in the corresponding coefficient latch circuit of the spatial filter operation unit 6, and the multiplier corresponding to the coefficient latch circuit. Set the coefficient to. The comparison result is output from the comparator 5 on a pixel-by-pixel basis, and the operation described above is executed every time the comparison result is output.
The coefficient of 7 is changed. When the brightness is high, the coefficient signal is read from the second register 8 and the spatial filter calculation unit 6
Set to.

In this way, the coefficient of the spatial filter calculation unit 6 is changed depending on whether the input image has low brightness or high brightness. Therefore, the luminance signal of the low-luminance portion of the input image is subjected to gradation correction by a coefficient suitable for the gradation correction of the low-luminance area, and the luminance signal of the high-luminance portion of the input image is suitable for gradation correction of the high-luminance area. The gradation correction is performed using the coefficient. As a result, the monitor 12
The gradation correction image displayed on the screen can obtain an image with gradation suitable for human visual characteristics.

FIG. 4 shows the luminance distribution of the input image before gradation correction and FIG. 5 shows the luminance distribution of the input image after gradation correction. As shown in the figure, when the filtering process according to the present embodiment is performed, the change in the brightness distribution differs between the low brightness region and the high brightness region.

As described above, according to the present embodiment, the coefficient of the spatial filter calculating section 6 can be changed between the low-luminance side and the high-luminance side with the reference value given to the comparator 5 as a boundary. It is possible to obtain an image with gradation suitable for visual characteristics.

In the configuration of the above embodiment, for example, a coefficient signal for setting the coefficient as shown in FIG. 6 is set in the first register 7 and the second register 8 is set to the coefficient signal of the above embodiment. The same high brightness coefficient is set.

The 7 × 7 coefficient shown in FIG. 6 has both the effect of removing noise and the effect of enhancing an image. Therefore, if the above coefficients are set in the register in advance, noise is reduced by smoothing by the coefficient shown in FIG. 6 in the low brightness region where noise is noticeable and sensitive to changes in brightness, and S / N is improved. Is also planned. Further, in the high-luminance region, optimum gradation correction is performed as in the above embodiment.

The coefficients stored in the first register 7 and the second register 8 are arbitrary, and depending on the value of the coefficient, various processing functions can be provided in addition to simple tone correction. The coefficient shown in FIG. 6 has a noise reduction function by smoothing as described above.

In the above embodiment, the number of reference values set in the comparator is one, so the coefficients are changed in two areas, the low brightness area and the high brightness area. Only finer coefficient changes are possible.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, three reference values 1 to 3 are set in the comparator 5'to generate four kinds of output signals according to the brightness value, and the coefficient register group 24 is set to each of the first to the fourth. Of the registers 31 to 34. The selector 9'selects one register from the first to fourth registers 31 to 34 according to the output of the comparator 5 '. Other configurations are the same as those of the device shown in FIGS. Therefore, the same parts are designated by the same reference numerals to avoid redundant description.

For example, a coefficient suitable for smoothing processing is set in the first register 31, a coefficient suitable for gradation correction in the low luminance region is set in the second register 32, and the third register 3 is set.
3 is set to a coefficient suitable for gradation correction in the high brightness area, and the fourth
A coefficient for emphasizing gradation is set in the register 34.

Then, the first register 31 is selected in the area where the brightness value of the input image is the reference value 1 or less, and the second register 32 is selected in the range of the reference value 1 to the reference value 2. In the range of the reference value 2 to the reference value 3, the third register 33 is selected,
In the area exceeding the reference value 3, the fourth register 34 is selected.

According to the embodiment configured as described above, the luminance area of the input image can be detected separately into four areas.
You can apply arbitrary corrections to each of the areas,
Finer gradation correction than that of the above-described embodiment can be performed.

FIG. 8 shows the brightness distribution before gradation correction and the setting positions of three reference values, and FIG. 9 shows the brightness distribution after gradation correction. As shown in these two figures, changes in the luminance distribution before and after correction in the four regions divided by the three reference values 13 are different from each other.

In the above embodiment, the reference value is set in the comparator 5'from the CPU 10, but the luminance signal output from the A / D converter 2 is used as the reference value as shown in FIG. It is also possible to take in the generation unit 40 and calculate three reference values from the luminance signal there and give them to the comparator 5 ″. With this configuration, it is possible to set the reference value corresponding to the change in the brightness of the input image, and it is possible to realize finer image correction.

Next, FIG. 11 shows the third embodiment of the present invention.
Will be described with reference to. The same parts as those in the first embodiment described above are designated by the same reference numerals. The comparator 5 is set with seven reference values Y1 to Y7 that divide a 10-bit gradation luminance region into eight, and outputs a comparison result signal (coefficient selection signal) corresponding to the luminance value of the input image.

The spatial filter block 4 includes the first to the seventh
The blocks 21-1 to 21-7 are each composed of seven coefficient register groups 24-1 to 24-7 as in the first embodiment. Each coefficient register group 24-1 to 24-7 is a register 7
-1 to 7-8. These registers 7-
Coefficient signals 1 to 7-8 are applied to the luminance regions divided into eight by the comparator 5 to perform gradation enhancement suitable for each luminance. In this embodiment, the brightness of the input image is Y1.
When the luminance is less than (minimum luminance) or less than Y7 (maximum luminance value), the degree of gradation enhancement is strongest, and the luminance of the input image is Y3 to Y5.
In this case, the coefficient signal that makes the gradation enhancement weakest is stored.

Selector 9 (selectors 25-1 to 25-
7) is the register 7-1 of the corresponding coefficient register group.
7-8, the register is selected according to the coefficient selection signal from the comparator 5, and the coefficient signal of the selected register is sent to the corresponding multiplication unit of the spatial filter operation unit 6. For example, when a coefficient selection signal corresponding to the reference value Y1 from the comparator 5 is input, 7 × 7 in total from each register 7-1 of each coefficient register group in each block.
The coefficient pattern of is read. Similarly, the registers 7-2 to 7-8 are selected according to the coefficient selection signals Y2 to Y7. One coefficient pattern is configured with the same register number of each register group in each block.

Further, in this embodiment, a gradation compression unit 50 for compressing 10-bit gradation to 8-bit gradation is provided at the output stage of the spatial filter calculation unit 6. Next, the operation of this embodiment configured as described above will be described. Since the basic operation of the spatial filter unit 4 is the same as that of the first embodiment, a different operation will be described here.

An image signal is input to a delay unit 3 including a spatial filter calculation unit 6 and six line memories, and a comparator 5
The luminance signal of the input image is input to. The comparator 5 compares the brightness value of the input image with the reference values Y1 to Y7 to detect the brightness value of the input image, and outputs a coefficient selection signal according to the detected brightness value.

The selector 9 selects a corresponding register from the coefficient register group based on the coefficient selection signal input from the comparator 5. For example, if the brightness value of the input image is Y1 or less or Y7 or more, the register in which the filter operation coefficient with the highest degree of gradation enhancement is stored as a coefficient signal is selected. The brightness value of the input image is Y3 to Y.
If it is 5, a predetermined register in which the coefficient signal of the filter calculation coefficient that weakens the degree of gradation enhancement is stored is selected.

7 × selected according to the brightness value of the input image
The coefficient signals forming the coefficient pattern of No. 7 in each block are transmitted through the coefficient latches 26-1 to 26-7 to the multipliers 23-1 to 23-1.
Given to 23-7. Since the coefficient selection signal is output from the comparator 5 on a pixel-by-pixel basis, the filter operation coefficient of 7 × 7 is changed on a pixel-by-pixel basis in all blocks.

In the adder 20, the sum of the multiplication results output from the multipliers of the blocks 21-1 to 21-7 in the spatial filter operation unit 6 is obtained. For example, in the case of a 10-bit gradation input image as shown in FIG. 12A, the spatial filter operation unit 6 performs 7 × 7 filtering processing in which the coefficient is changed according to the brightness value, Different gradation correction is performed in each brightness area,
In the high-luminance region (near 10 bits) as shown in FIG. 12B, the signal has gradation enhancement.

The output of the spatial filter calculation unit 6 is input to the gradation compression unit 50. The gradation compression unit 50 has a reference value Y given to the comparator 5 for dividing the luminance region into eight.
A conversion table as shown in FIG. 13 which is approximated to a polygonal line having 1 to Y7 as inflection points is set. This conversion table has a logarithmic change in which the compression ratios of the regions corresponding to the low-luminance portion and the high-luminance portion are higher than those of the other regions in accordance with the human visual characteristics. Such a conversion table is CPU1
It is given in advance from 0.

The output of the spatial filter calculation unit 6 is shown in FIG.
The gradation is compressed according to the conversion table shown in FIG. Here, when gradation conversion is performed using the conversion table shown in FIG. 13, gradation information is normally destroyed due to high compression ratios in the low-luminance portion and the high-luminance portion, but as described above in the present embodiment. Since the gradation enhancement is performed more strongly in the low-luminance portion and the high-luminance portion, the gradation information does not deteriorate. Therefore, the gradation compression unit 50 outputs an image signal as shown in FIG. 12C that is gradation-compressed from 10-bit gradation to 8-bit gradation without degrading the gradation information.

As described above, according to the present embodiment, since the gradation enhancement is performed by the spatial filter calculation unit 6 in consideration of the characteristics of the conversion table when the gradation compression is performed, the gradation information of the input image is calculated. It is possible to perform gradation compression without deterioration.

Since the filter calculation coefficient set in the spatial filter calculation unit 6 is arbitrary, the degree of gradation correction is changed between the low-luminance portion and the high-luminance portion of the input image so as to suit human visual characteristics. It is also possible to perform gradation correction so that the high-luminance portion is emphasized over the low-luminance portion.

It is also possible to add a function such as noise removal to the filtering process. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0054]

As described above in detail, according to the image processing apparatus of the present invention, since the coefficient of the spatial filter is changed according to the brightness of the input image, the gradation matching the human visual characteristics is obtained. It is possible to realize not only the correction but also an arbitrary filter function.

Further, according to the image processing apparatus of the present invention, the coefficient of the spatial filter is changed according to the brightness of the input image, and the filter output is gradation-compressed. Therefore, according to the brightness value of the input image. The degree of gradation enhancement can be changed, and gradation can be compressed without degrading the gradation information of the input image.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a spatial filter block provided in the image processing apparatus shown in FIG.

FIG. 3 is a block diagram of one block of the spatial filter block shown in FIG.

FIG. 4 is a diagram showing a luminance distribution of an input image before gradation correction in the first embodiment.

FIG. 5 is a diagram showing a luminance distribution of an input image after gradation correction in the first embodiment.

FIG. 6 is a diagram showing coefficients set in a spatial filter calculation unit of the image processing apparatus according to the first embodiment.

FIG. 7 is a functional block diagram of an image processing apparatus according to a modified example of the first embodiment.

FIG. 8 is a diagram showing a luminance distribution of an input image in another modification of the first embodiment.

FIG. 9 is a diagram showing a luminance distribution of an input image after gradation correction according to another modification of the first embodiment.

FIG. 10 is a diagram showing a configuration in which a part of another modification of the first embodiment is further modified.

FIG. 11 is a configuration diagram of an image processing apparatus according to a second embodiment of the present invention.

FIG. 12 is a diagram showing a gradation change of an input image in the second embodiment.

FIG. 13 is a diagram showing a conversion table for gradation compression.

FIG. 14 is a diagram for explaining a conventional gradation correction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Camera, 2 ... A / D converter, 3 ... Delay part, 4 ... Spatial filter block, 5 ... Comparator, 6 ... Spatial filter calculation part, 7 ... 1st register, 8 ... 2nd register, 9
... selector, 10 ... CPU, 50 ... gradation compression unit.

Claims (2)

[Claims] 1. An image processing apparatus for inputting an image signal having a brightness value corresponding to an original image, performing a filtering process on the image signal, and performing a desired gradation correction. A coefficient is set, each coefficient is changed in at least one pixel unit according to a coefficient signal, and a spatial filter for performing spatial filtering processing on the image signal, and for setting each coefficient in the spatial filter Coefficient storage means in which a plurality of coefficient signals are stored, comparing means for detecting the brightness value of the image signal input to the spatial filter, and comparing the detected brightness value with at least one reference value preset The coefficient signal of the coefficient storage unit is selectively applied to the spatial filter in each of the high-luminance part and the low-luminance part of the image signal based on the comparison result of the comparison means. The image processing apparatus characterized by that comprising a selection means. 2. An image processing apparatus for inputting an image signal having a luminance value corresponding to an original image, performing a filtering process on the image signal, and performing a desired gradation correction, in at least one pixel unit filtering operation. A coefficient in the i-th row and j-th column that can be changed in synchronization with the operation is set, the image signal is input in the state of the pixel matrix in the i-th row and the j-th column, and filtering processing is performed by the coefficient with the pixel of interest in the pixel matrix as the center. A spatial filter, a coefficient storage unit that stores a plurality of sets of coefficient patterns of i rows and j columns to be set in the spatial filter, a brightness value of an image signal input to the spatial filter, and the detected brightness value. Comparing means for comparing at least one preset reference value and outputting a predetermined coefficient selection signal according to the comparison result; Coefficient selection means for selecting a coefficient pattern from the coefficient storage means based on the selected coefficient selection signal, and setting the selected coefficient pattern in the spatial filter; and gradation compression for the signal output from the spatial filter. An image processing apparatus comprising: a gradation compression unit that performs processing.